Existing transponder devices such as Radio Frequency IDentification (RFID) tags require either a self-contained power supply, RF energy transmitted from an interrogator, or both to operate. This typically requires close proximity to the interrogator or higher-power RF transmissions. In many environments this is neither feasible nor desirable.
While active RFID tags respond using energy derived from a battery on the tag, this limits tag life to the life of the battery or requires access to the tag to replace batteries as they drain. Tag access is not feasible or possible for many applications. Passive tags not require batteries, but do require RF interrogation signals of sufficient power and duration to enable them to generate the RF response signal. This limits the range over which tags can operate and can cause interference when interrogation signals are at higher powers.
Similarly, sensors that wirelessly communicate their data are limited in range and lifespan. These constraints eliminate applications requiring multiple, inaccessible RF transponder devices.
What is needed, therefore, are techniques for employing ambient radiation to power devices such as sensors and RFID transponders.